Process of treating waste liquors from soda-pulp mills.



UNITED STATES PATENT OFFICE.

nan: LUIDVIG RINMAN, or naRNAs, swnnnn.

PROCESS OF TREATING WASTE LIQUORS FROM SODA-PULP MILLS.

Specification of Letters Patent.

Ho Drawing. Application flied January 27., 1911. Serial No. 805,095.

To all whom it may concern:

. therefrom,,of which the fol owing is a spec fication.

Black li mm from soda pulp mills that freed, wholly or to a considerable extent, fromthose organic substances which are precipitated-by. carbonic acid, whether the separation of the said substances be erformed by treatment with carbonic sci or otherwise, contain besides sodium oxid combined -with carbonic acid or acids weaker than carbonic acid, also sodium oxid combined with acetic acid,formic acid, resinous acids and other organic acids.

The object of the invention is to provide a process of regenerating caustic soda and recovering the organic acids contained in the said liquors.

The invention consists, chiefly, in saturating. the liquor, after concentrating the same, if required, with carbonic acid at a. temperaturefavorable for the-formation of'bicarbonate of soda. Such a temperature lies between 15-and 40 centigrade. The output of bicarbonate of soda precipitated is increased as the liquor is concentrated. At

i all events, the liquor cannot be concentrated more than to tlie consistency of sy'rup,since in such case it would not be possible to separate the bicarbonate by filtration. The saturation with carbon dioxid enerally requires to the concentration of the carbon dioxid). The precipitate of bicarbonate of soda ma be employed, after washing or unwashe, for producing boiling-lye. The filtrate remaining after the precipitation of the bicarbonate of soda may thereupon be further treated by adding to it, a stronger acid, such asoxalic, hydrochloric, sulfuric, or phosphoric acid, whereby the organicacids are disen aged, As to the latter, the acetic acid and t e formic acid may be separated by distillation, being obtainable separately or together, as may be desired. Thus, for instance, the filtrate may first be partially acidified with the stronger acid, the quantity of acid equivalent to half the quantity or somewhat less than half the quantity of sodacombined with carbon dioxid and organic acids, in which case the acetic acid is isengaged and may be distilled ofl, while the stronger formic acid remains in combination with sodium with after distilling oil the acetic acid the resldue is completely Patented Feb. 13, 1912.

acidified for disengaging the formic acid.

i t e The resinous acids, y have not been separated" (by filtration, skimmin or otherwise) before or during the disti lat-ion of acetic acid and formic acid, remain together with 5 mp substances soluble in water. and the so asa ts of the acid or acids employed. If desired, this residue may be heated to about 200centigrade, whereby the organic acids give oil water and carbonic acid, said heating bein continued as long as gas is developed. y this treatment the organic acids are entirely resinized, so that they will become insoluble in water. The mass of salt may thereupon be easily separated from the resins by washing the mass with water, preferably hot, by which it is dissolved while the resins remain undissolved. The residue'after distillation may, obviously, be treated with alcohol or other suitable solvent for the organic substances until these substances have been dissolved, whereupon they may be separated from the salts by any suitable methods. As a suitable solvent instead of alcohol small quantities of water,

' will be complete, if the substances. engaged in the same are calculated from the formula. If the solution contains suflicient quantities of hi hly dissociated salts, such as sodium chlorld, the sodium oxalate formed in the reaction is completely precipitated, even in warm solution, as a fine crystallirye powder,

so that the solution of acetic acid, formic acid, etc., whichis chemically free from oxalic acid, may be separated from the oxalate without any quantity thereof being lost. If

desired, this oxalate may be washed with water, the wash-water being suitably used for dissolving further quantities o. oxalic acid. .Ily treating the sodium .oxalate with caustic lime soda lye for boiling cellulose matters and calcium oxalate for producing new quantities of oxalic acid may be produced. In causticizing the sodium oxalate the crystal mass thereof may by stirring be converted directly into somewhat more than the calculated quantity of lime-Wash oi oidinary temperature. If the oxalate per liter of lime-wash oes not exceed 70 gr. of Na,O a'complete reaction with tamed can be employed for boiling cellulose substances if the presence of sodium chlorid does not constitute an obstacle. By this means the further advantage is gained that the chlorin and hydrogen obtained are transformable into hydrochloric acid which may be emplo ed ,for acidifying further uantities of lack li uor. The sodium c lorid may also be us 'for producing carbonate of soda by means of the ammoniasoda process. The procedure is advantageous particularly on account of its not be mg necessary to free the carbonate of soda obtained from sodium chlorid. and on account of it being possible to produce at the same time carbonate of soda from new quantities of sodium chlorid in order to cover uantity of 'ing the substances capable of ,beingprecipitated by completely the loss of carbonate of soda in boiling cellulose substances with such a cheap suliferous solution of carbonate of soda. Moreover, the bicarbonate oi. soda obtained, which contains ammonia and carbonic acid, need not be calcined but may be freed from ammonia and carbonic acid in solution, which is considerably cheaper. If, on the other hand, sulfuric acid is used for disengaging the organic acids, carbonate of soda may, obviously, be recovered by the Le Blane process from the sulfate obtained. The solution of carbonate of soda obtained is ceusticized directly to produce boilinglye for boiling cellulose substances. Finally, if phosphoric acid is used for disengaging the organic acids, the sodium phosphate obtained may be treated with time for prli ducing-dircctly soda-lye for boiling cellulose substances and at the same time obtaining calcium phosphate. The phosphoric acid is thereupon regenerated in known manner from the calcium phosphate by means of sulfuric acid. I' claim: The process of treating black liquors from soda pulp iquor substantially from organic carbonic acid, and thereupon precipitating bicarbonate of soda by saturating the liquor with carbonic acid ata suitable concentra:

tion and ,a suitable temperature of the.

liquor.

ERIK LUDVIG RINMAN.

Witnesses HENRY PERSON, I WALEN TIN BERGGREN.

mills, which consists in first free- 

